the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 Feb 2024
The effects of orbital forcing on the East Asian Summer Monsoon for the past 450 kyr
Abstract. Understanding orbital-scale changes in East Asian summer monsoon (EASM) precipitation is a fundamental issue in paleoclimate research for assessing the response of the East Asian monsoon to different climate forcings, such as insolation, ice volume, and greenhouse gases. However, owing to the inconsistencies between different proxies, the fundamental driving force for EASM variability remains controversial. In the present study, the global climate under the given insolation changes over the past 450 kyr was calculated using a climate model, Meteorological Research Institute Coupled General Circulation Model version 2.3 (MRI–CGCM2.3). The calculated change in summer precipitation is dominated by a 20-kyr precession cycle over China, highly consistent with cave δ18O records in southeast China. The proxy data from northern China (Chinese Loess Plateau) and Japan (Lake Biwa) cannot be fully explained by the calculation results, implying the importance of other forcing such as ice-sheet volume. A strong positive correlation was observed between insolation and precipitation over the coastal area of China and a negative correlation between insolation and precipitation around Japan. The results imply that the EASM is affected by the insolation intensity; however, the effect can vary between regions. The positive correlation between boreal summer insolation and precipitation over China results from the atmosphere-ocean interaction over the Indian Ocean and the western Pacific. Under intense insolation, the northern shift of the monsoon front associated with the intensification of the North Pacific subtropical high causes an increase in rainfall in the coastal area of China. The intensification of the subtropical high is caused by the integration of local wind–evaporation–sea surface temperature (WES) feedback with the Kelvin wave response to the warm Indian Ocean (IPOC mode). In contrast, the EASM intensity around Japan was affected by the strength of the North Pacific High. Under strong insolation, the North Pacific High intensified, causing a decrease in summer precipitation around Japan.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-307', Anonymous Referee #1, 07 Mar 2024
General comments:
The work titled "The Effects of Orbital Forcing on the East Asian Summer Monsoon for the Past 450 kyr" is intriguing. The authors have adeptly reviewed previous research progress and provided a detailed and clear explanation of the research methodology in this paper. However, the section discussing their own research findings appears to be rather weak, lacking a comprehensive showcase of the work's novel discoveries. Substantial revisions are necessary to better highlight the new contributions of the study.
Specific comments to the authors
The term "calculate and calculation" in the given sentence (Abstract) is not accurate; it should be replaced with "simulated" or "simulation." Please check similar issue thorough the manuscript.
The initial segment of the abstract is well-structured; however, the latter part, starting from "The calculated change in summer precipitation is dominated by a 20-kyr precession cycle over China, highly consistent with cave d18O records in southeast China," becomes overly generalized. The author delves into various aspects, addressing the periodicity of simulated East Asian Summer Monsoon (EASM) precipitation in connection with forcing cycles. Subsequently, a correlation analysis is presented to establish the relationship between EASM precipitation intensity and solar radiation forcing. This deviates somewhat from the conventional approach of enhancing mechanistic understanding through numerical simulations. Therefore, in this section, I recommend that the author enrich the paper by incorporating more explanations related to climate dynamics.
The Introduction section lacks a recent review of the advancements in the comparison of data and models in East Asian paleomonsoonal dynamics.
Sun, Y., H. Wu, G. Ramstein, B. Liu, Y. Zhao, L. Z. X. Li, X. Y. Yuan, W. C. Zhang, L. J. Li, L. W. Zou, T. J. Zhou. Revisiting the Physical Mechanisms of East Asian Summer Monsoon Precipitation Changes During the Mid-Holocene: A Data–model Comparison. Climate Dynamics 60, 1009–1022 (2023). https://doi.org/10.1007/s00382-022-06359-1.
Sun, Y., H. Wu, M. Kageyama, G. Ramstein, L. Z. X. Li, N. Tan, Y. T. Lin, B. Liu, W. P. Zheng, W. C. Zhang, L. W. Zou, T. J. Zhou. 2021. The contrasting effects of thermodynamic and dynamic processes on East Asian summer monsoon precipitation during the Last Glacial Maximum: a data-model comparison. Climate Dynamics. 56, 1303–1316.
Sun, Y., G. Ramstein, L. Z. X. Li, C. Contoux, N. Tan, T. J. Zhou. 2018. Quantifying East Asian summer monsoon dynamics in the ECP4.5 scenario with reference to the mid‐Piacenzian warm period. Geophysical Research Letters, 45: 12,523–12,533.
I could not agree with the authors statements “Section 4 discusses the possible climate systems that drive EASM variability”. As we knew, orbital forcing via solar radiation changes can be attributed fundamental driver of climate changes, here the authors may discuss the possible climate systems associated with EASM variability.
L86: “due to orbital forcing” needs to put behind the insolation changes
L131-135 should move to the method section somewhere.
Title in section 3.1 is confusing, if I understand well the authors want to express “simulated……”?
I have additional comments on the organization of the results section. In fact, it is not necessary to divide Section 3 into two subsections. The authors intend to focus on one specific task in this section: the model-data comparison of East Asian Summer Monsoon (EASM) precipitation evolution for the last 450,000 years. The current version contains numerous citations, making it challenging for the reader and reviewer to discern the extent of the authors' new findings. Consolidating the section into a single subsection may help clarify the presentation and emphasize the novel contributions of the authors. Please rephase these sections.
Figure.4-5-6 can be merged into one new Figure.
L427: please use SEC instead South East China, as the abbreviation has already appeared.
- AC2: 'Reply on RC1', Mariko Harada, 02 May 2024
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RC2: 'Comment on egusphere-2024-307', Anonymous Referee #2, 10 Mar 2024
This paper presented new results about how orbital forcing influence the East Asian Summer Monsoon by a group of new time-slice simulations. The authors conducted an extensive review of previous research. But more discussion should be added regarding their own results. (1)They only presented summer precipitation changes. But for East Asian summer monsoon, annual precipitation and summer temperature could also be presented and compared with proxy records; (2) They only show three proxy records. More model-proxy comparison should be added. The abstract is a bit confusing and should be rewritten. In general, the paper requires extensive revision before it can be considered for publication.
Line 18 'Calculated' should be 'Simulated'. Similar expressions throughout the text need to be modified.
Line 41 23 kyr periodicity should be 23-kyr periodicity. Similar expressions throughout the text need to be modified, e,g. line 43.Line 34 Reference should be (An et al., 2015)
Line 46 Logic question. How does 'EASM varies in phase with orbital cycles' suggest 'the EASM is affected by changes in ice volume'? The author seems to confuse ‘100-kyr cycle' and 'eccentricity cyle'.
Line 52 Rewrite the sentence.
Line 61 Rewrite the sentence.Line 20 I do not agree that the results can come to the conclusion ... the importance of other forcing (e.g. ice sheet). Besides external forcings, the internal feedback should also be considered.
Line 97 This model comprises an atmospheric general circulation model (AGCM) and a global ocean general circulation model (OGCM). This sentence could be deleted because everyone knows that a coupled GCM consists of AGCM and OGCM.
More introduction on the model should be added, e,g, if there is ice-sheet model.Line 171 Why is the 100-kyr band from eccentricity? Why not ice volume?
Citation: https://doi.org/10.5194/egusphere-2024-307-RC2 - AC1: 'Reply on RC2', Mariko Harada, 02 May 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-307', Anonymous Referee #1, 07 Mar 2024
General comments:
The work titled "The Effects of Orbital Forcing on the East Asian Summer Monsoon for the Past 450 kyr" is intriguing. The authors have adeptly reviewed previous research progress and provided a detailed and clear explanation of the research methodology in this paper. However, the section discussing their own research findings appears to be rather weak, lacking a comprehensive showcase of the work's novel discoveries. Substantial revisions are necessary to better highlight the new contributions of the study.
Specific comments to the authors
The term "calculate and calculation" in the given sentence (Abstract) is not accurate; it should be replaced with "simulated" or "simulation." Please check similar issue thorough the manuscript.
The initial segment of the abstract is well-structured; however, the latter part, starting from "The calculated change in summer precipitation is dominated by a 20-kyr precession cycle over China, highly consistent with cave d18O records in southeast China," becomes overly generalized. The author delves into various aspects, addressing the periodicity of simulated East Asian Summer Monsoon (EASM) precipitation in connection with forcing cycles. Subsequently, a correlation analysis is presented to establish the relationship between EASM precipitation intensity and solar radiation forcing. This deviates somewhat from the conventional approach of enhancing mechanistic understanding through numerical simulations. Therefore, in this section, I recommend that the author enrich the paper by incorporating more explanations related to climate dynamics.
The Introduction section lacks a recent review of the advancements in the comparison of data and models in East Asian paleomonsoonal dynamics.
Sun, Y., H. Wu, G. Ramstein, B. Liu, Y. Zhao, L. Z. X. Li, X. Y. Yuan, W. C. Zhang, L. J. Li, L. W. Zou, T. J. Zhou. Revisiting the Physical Mechanisms of East Asian Summer Monsoon Precipitation Changes During the Mid-Holocene: A Data–model Comparison. Climate Dynamics 60, 1009–1022 (2023). https://doi.org/10.1007/s00382-022-06359-1.
Sun, Y., H. Wu, M. Kageyama, G. Ramstein, L. Z. X. Li, N. Tan, Y. T. Lin, B. Liu, W. P. Zheng, W. C. Zhang, L. W. Zou, T. J. Zhou. 2021. The contrasting effects of thermodynamic and dynamic processes on East Asian summer monsoon precipitation during the Last Glacial Maximum: a data-model comparison. Climate Dynamics. 56, 1303–1316.
Sun, Y., G. Ramstein, L. Z. X. Li, C. Contoux, N. Tan, T. J. Zhou. 2018. Quantifying East Asian summer monsoon dynamics in the ECP4.5 scenario with reference to the mid‐Piacenzian warm period. Geophysical Research Letters, 45: 12,523–12,533.
I could not agree with the authors statements “Section 4 discusses the possible climate systems that drive EASM variability”. As we knew, orbital forcing via solar radiation changes can be attributed fundamental driver of climate changes, here the authors may discuss the possible climate systems associated with EASM variability.
L86: “due to orbital forcing” needs to put behind the insolation changes
L131-135 should move to the method section somewhere.
Title in section 3.1 is confusing, if I understand well the authors want to express “simulated……”?
I have additional comments on the organization of the results section. In fact, it is not necessary to divide Section 3 into two subsections. The authors intend to focus on one specific task in this section: the model-data comparison of East Asian Summer Monsoon (EASM) precipitation evolution for the last 450,000 years. The current version contains numerous citations, making it challenging for the reader and reviewer to discern the extent of the authors' new findings. Consolidating the section into a single subsection may help clarify the presentation and emphasize the novel contributions of the authors. Please rephase these sections.
Figure.4-5-6 can be merged into one new Figure.
L427: please use SEC instead South East China, as the abbreviation has already appeared.
- AC2: 'Reply on RC1', Mariko Harada, 02 May 2024
-
RC2: 'Comment on egusphere-2024-307', Anonymous Referee #2, 10 Mar 2024
This paper presented new results about how orbital forcing influence the East Asian Summer Monsoon by a group of new time-slice simulations. The authors conducted an extensive review of previous research. But more discussion should be added regarding their own results. (1)They only presented summer precipitation changes. But for East Asian summer monsoon, annual precipitation and summer temperature could also be presented and compared with proxy records; (2) They only show three proxy records. More model-proxy comparison should be added. The abstract is a bit confusing and should be rewritten. In general, the paper requires extensive revision before it can be considered for publication.
Line 18 'Calculated' should be 'Simulated'. Similar expressions throughout the text need to be modified.
Line 41 23 kyr periodicity should be 23-kyr periodicity. Similar expressions throughout the text need to be modified, e,g. line 43.Line 34 Reference should be (An et al., 2015)
Line 46 Logic question. How does 'EASM varies in phase with orbital cycles' suggest 'the EASM is affected by changes in ice volume'? The author seems to confuse ‘100-kyr cycle' and 'eccentricity cyle'.
Line 52 Rewrite the sentence.
Line 61 Rewrite the sentence.Line 20 I do not agree that the results can come to the conclusion ... the importance of other forcing (e.g. ice sheet). Besides external forcings, the internal feedback should also be considered.
Line 97 This model comprises an atmospheric general circulation model (AGCM) and a global ocean general circulation model (OGCM). This sentence could be deleted because everyone knows that a coupled GCM consists of AGCM and OGCM.
More introduction on the model should be added, e,g, if there is ice-sheet model.Line 171 Why is the 100-kyr band from eccentricity? Why not ice volume?
Citation: https://doi.org/10.5194/egusphere-2024-307-RC2 - AC1: 'Reply on RC2', Mariko Harada, 02 May 2024
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Taiga Matsushita
Mariko Harada
Hiroaki Ueda
Takeshi Nakagawa
Yoshimi Kubota
Yoshiaki Suzuki
Youichi Kamae
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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